Extrusion press



y 26, 1966 H. B. ALEXANDER 3,262,155

EXTRUSION PRESS Filed Dec. 30, 1963 2 SheetsSheet 1 Harvey B. Alexander INVENTOR.

MW BY ATTORNEY July 26, 1966 B. ALEXANDER 3,262,155

EXTRUSION PRESS Filed Dec. 30, 1963 2 Sheets-Sheet 2 Harvey B. Alexander INVENTOR.

38 BY MW ATTORNEY United States Patent 3,262,155 EXTRUSION PRESS Harvey B. Alexander, Indian Head, Md., assignor to the United States of America as represented by the Secretary of the Navy Filed Dec. 30, 1963, Ser. No. 334,673 3 Claims. (Cl. 1812) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates to an extrusion press for use in the production of solid propellants. More particularly, the invention concerns an extrusion press for use in producing high-energy solid propellants which, because of their high sensitivity, are specially hazardous to manufacture.

In the conventional extrusion operation, as performed in the production of solid propellants, the propellant composition, which typically is a moldable plastic material somewhat like putty, is forced through a die, or a multiple of dies operating in parallel, to produce strands of tubular or rod-like form. The aforementioned die or dies comprise a part of the extrusion press. The press consists also of a cylindrical confining chamber which holds the propellant mass to be extruded, and a ram which acts on the propellant in response to an externally applied force, causing extrusion to take place.

An extrusion press of this type has the inherent disadvantage that the small, annular clearance space between the ram and the cylinder wall presents a hazardous zone. Propellant usually is forced into this zone during operation of the press and thereupon is subjected to high shearing force. This force, acting as the ram moves, may produce local heat concentrations of suflicient intensity to raise the propellant to the ignition point. Moreover, it is difiicult to control the precision of alignment of the ram in the cylinder, and if the degree of misalignment becomes great enough, the ram will rub against the cylinder wall. The metal-to-metal friction produced in this manner is considered very dangerous relative to starting ignition of the propellant.

In the extrusion press embodiment in this invention, the aforementioned hazardous zone is eliminated by a new design feature which permits the extrusion force to be applied to the propellant by a hydraulic fluid instead of by a rigid body, such as the conventional ram. Intermixing of the hydraulic fluid with the propellant is prevented by an elastic membrane positioned so as to separate the hydraulic fluid from the propellant at all times.

It is, therefore, an object of this invention, to provide a new and improved extrusion press for use in producing high-energy solid propellants which affords a maximum degree of safety from the hazard of propellant ignition.

Another object of the invention is to provide a new and improved extrusion press for use in producing highenergy solid propellants which is free of metal-to-metal friction and produces only negligible heat concentrations in the area of the propellant, thus reducing the likelihood of propellant ignition.

Still another object of this invention is to produce an extrusion press for producing high-energy solid propellants which employs a fluid piston for applying an extruding force to the propellant that is at all times separated from actual contact with the propellant.

Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings wherein:

FIG. 1 is a sectional side elevation of one embodiment of an extrusion press embodying the invention;

FIG. 2 is a sectional view of the embodiment illustrated in FIG. 1 taken along line 22 therein;

FIG. 3 is a partial section of another embodiment; and

FIG. 4 is a perspective view of a third embodiment of the invention.

Referring more particularly to the accompanying drawings and, for the present, to FIGS. 1 and 2, there is shown an extrusion press 10 having a cylinder 11 which forms the central part of the assembly. The cylinder may be of any usual type and material used in connection with conventional presses. Within the cylinder 11 is a piston 12 fitted with an O-ring annular gasket fluid seal 13 and connected by a rod 14 passing through an aperture 15 in cap 16, shown in threaded engagement with cylinder 11, to a source of motive power (not shown). This power source is of such nature as to impart translatory motion to the piston 12 in a controllable manner such as to effect the desired operation of the press 10, and may be a double-acting hydraulic ram or any other equivalent unit which is capable of imparting forward and reverse motions to the piston 12.

The material 17 is a hydraulic fluid which has the function of transmitting the motion of the piston 12 to an elastic diaphragm 18. The hydraulic fluid 17 may be a petroleum oil, a glycol-Water solution, or virtually any liquid which has a low vapor pressure, a low-to-moderate viscosity, and which produces little or no chemical attack on the materials with which it comes in contact in the extrusion press 10. The elastic diaphragm 13 is clamped tightly about its periphery to an annular flange 19 on cylinder 11 by an annular sealing and clamping ring 20 secured through the diaphragm to the cylinder flange by screws 21, and serves with the piston 12 to contain the hydraulic fluid 17 within the press cylinder 11. As the diaphragm 18 is to be as elastic as possible, a preferred material of fabrication is gum rubber or a selected synthetic rubber. In addition to providing a means of containment of the hydraulic fluid 17, the diaphragm 18 functions to transmit force applied on the hydraulic fluid to the propellant 22, which is the material to be extruded in operation of the press. A perforated plate 23 is positioned within cylinder 11 so as to control the shape of the diaphragm 18 when the diaphragm is in the condition of maximum tensile stress, thus flattening the dome-shape which the diaphragm otherwise would assume and thereby defining a more nearly cylindrical cavity on the lower side of the diaphragm, as illustrated more clearly in FIG. 1. The resulting shape is advantageous to loading cylindrically shaped charges of propellant 22 into the press. Perforated plate 23 may be attached to the inner wall of cylinder 11 by welding, or by any other suitable means.

The propellant 22 is extruded through a die assembly 24 having an orifice 25 therein for that purpose. It is to be understood that this die assembly 24 is not necessarily limited to a single orifice 25, as shown, but may comprise a plurality of apertures, all of which produce simultaneously the desired form of extruded propellant. Likewise, the size and cross-section configuration of the orifice will be subject to variation, depending on the size and geometry of the extruded product.

In the embodiment illustrated in FIG. 1 the die as sembly 24 is fixed to the cylinder 11 by a plurality of bolts 26 passing through apertures in the die assembly 24, the annular gasket 20, and the flange portion 19 of cylinder 11, and secured thereon by wing nuts 27.

Following is a description of the normal cycle of operation of the aforedescribed extrusion press. The press 10 is made ready to receive the propellant charge by removing the end closure or die assembly 24 and moving the piston 12 to the end of its stroke in the direction tending to stretch the elastic diaphragm 18. The propellant charge 22, preferably in the form of a cylindrical block, is placed in the cavity formed by distention of the diaphragm 18 and closure 24 is secured in the closed position. Force is applied to the piston 12 in a direction to compact the propellant and cause it to extrude through the orifice 25 in closure 24. This extrusion of the propellant is the objective to be obtained in operation of the press 10. When the quantity of propellant 22 extruded has been suflicient to permit the elastic diaphragm 18 to return to a substantially plane configuration, the extrusion cycle is considered to be finished. A new extrusion cycle may then be commenced by removing the closure 24, charging the press with a new block of propellant 22, and continuing to operate the press in the sequence of the steps described above.

In the embodiment of FIG. 3, the die assembly or closure 24 is replaced by an internally threaded screw cap 28. With this arrangement, the nut-bolt locking means 26, 27 of the embodiment illustrated in FIG. 1 are not needed, and the outer peripheral wall of flange 19 on cylinder 11 is threaded as at 29 for threaded engagement with the screw cap 28. Screw cap 28 is provided with an orifice 25a. through which the propellant may be extruded.

In the embodiment illustrated in FIG. 4, a hinged cover 30 with a quick opening latch 31 provides the means for opening the extrusion press for the purpose of charging the press with a block or mass of propellant. The cover 30 is pivotally connected to lugs 32 on flange 19 of cylinder 11 by a right-angled protruding member 33 and pivot pin 34. Cover 30 is secured to flange 19 in the closed position by latch 31 which is pivotally connected to lugs 35 on cover 30 through pivot pin 36. Latch 31 pivots to an upright position between lugs 37 on cover 30 where it is secured by a wing-nut 38. The cover 30 is provided with an orifice 25b through which the propellant may be extruded.

It will be understood that .the motive power of the extrusion press described need not necessarily be restricted to that of a hydraulic ram. Thus, for example, it is equally satisfactory to operate the press by pumping the hydraulic fluid into and out of the press cylinder, according to the direction in which it is desired to cause motion of the diaphragm. Furthermore, applications of the extrusion press are considered in which it will be desirable to force the hydraulic fluid into the press cylinder in a pulsatory flow.

Furthermore, the diaphragm which separates the hydraulic fluid from the propellant charge need not be limited to the form of a plane sheet. Other shapes, such as that of a bellows, may be incorporated in the design of this part in order to produce greater extensibility without the development of correspondingly high stresses in the material of the diaphragm. This design feature is advantageous in enabling a comparatively large propellant charge to be extruded in a single extrusion cycle, and also it avoids the subjection of the diaphragm to high stress levels, tending thereby to prolong the working life of the diaphragm.

Obviously many other modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is: 1. An extrusion press for use in producing high-energy solid propellants comprising a cylindrical housing,

a piston reciprocably mounted in one end of said housing, said piston having an annular groove therein,

an O-ring fixed in said groove and movable with said piston to provide a fluid seal between said piston and said housing,

a closure for the other end of said housing having an aperture therein,

an elastic diaphragm fixed between said closure and the other end of said housing providing a fluid seal therebetween,

hydraulic fluid means in said housing between said piston and said diaphragm,

a perforated plate fixed within said housing in the region between said piston and said diaphragm and extending perpendicular to the wall surface of said housing,

said diaphragm being stretched so as to form a cupshaped portion when said piston is in its retracted position, said closure being removable to facilitate loading a block or mass of propellant into the cupshaped portion of said diaphragm,

and means for moving said piston within said housing whereby said fluid urges said diaphragm against said propellant and forces the propellants through the aperture in said closure.

2. An extrusion press according to claim 1 wherein said closure is pivotally connected to said housing and movable between open and closed positions thereon, and

means for locking said closure in the closed position.

3. An extrusion press according to claim 1 wherein said other end of said housing is externally threaded and said closure is an internally threaded substantially cylindrical cap adapted for threaded engagement therewith.

References Cited by the Examiner UNITED STATES PATENTS 409,734 8/1889 Criley 1812 720,902 2/1903 Du Bran 1812 2,128,241 8/1938 Goss. 2,264,146 11/1941 Crane 1812 X 2,272,880 2/1942 Greenup 18--8 2,770,836 11/1956 Hankey. 2,778,534 1/1957 Ramsey. 3,164,863 1/1965 Hunt 18--12 WILLIAM J. STEPHENSON, Primary Examiner.

L. S. SQUIRES, Assistant Examiner. 

1. AN EXTRUSION PRESS FOR USE IN PRODUCING HIGH-ENERGY SOLID PROPELLANTS COMPRISING A CYLINDRICAL HOUSING, A PISTON RECIPROCABLY MOUNTED IN ONE END OF SAID HOUSING, SAID PISTON HAVING AN ANNULAR GROOVES THEREIN, AN O-RING FIXED IN SAID GROOVE AND MOVABLE WITH SAID PISTON TO PROVIDE A FLUID SEAL BETWEEN SAID PISTON AND SAID HOUSING, A CLOSURE FOR THE OTHER END OF SAID HOUSING HAVING AN APERTURE THEREIN, AN ELASTIC DISPHRAGM FIXED BETWEEN SAID CLOSURE AND THE OTHER END OF SAID PROVIDING A FLUID SEAL THEREBETWEEN, HYDRAULIC FLUID MEANS IN SAID HOUSING BETWEEN SAID PISTON AND SAID DIAPHGRAM, A PERFORATED PLATE FIXED WITHIN SAID HOUSING IN THE REGION BETWEEN SAID PISTON AND SAID DIAPHRAGM AND EXTENDING PERPENDICULAR RO THE WALL SURFACE OF SAID HOUSING, SAID DIAPHRAGM BEING STRETCHED SO AS TO FORM A CUPSHAPED PORTION WHEN SAID PISTON IS IN ITS RETRACTED POSITION, SAID CLOSURE BEING REMOVABLE TO FACILITATE LOADING A BLOCK OR MASS OF PROPELLANT INTO THE CUPSHAPED PORTION OF SAID DIAPHRAGM, AND MEANS FOR MOVING SAID PISTON WITHIN SAID HOUSING WHEREBY SAID FLUID URGES SAID DIAPHRAGM AGAINST SAID PROPELLANT AND FORCES THE PROPELLANTS THROUGH THE APERTURE IN SAID CLOSURE. 